Transcript
  • *Organic Chemistry

    Organic Chemistry:

    Originally defined as study of compounds from living things / organisms (compounds from nature).Later, chemists made (synthesized) compounds in the laboratory

    NOW: Organic chemistry is the study of compounds containing carbon.

    However,Biochemistry is the study of the chemicals and processes that sustain life (the life on Earth that is based on carbon compounds).

    Biochemistry is based on and overlapped with Organic Chemistry.

  • Organic Chemistry*Over 10 million organic compounds have been identifiedabout 1000 new ones are discovered or synthesized and identified each day!Unlimited number of organic compounds are possibleWhy?C is a small atom it forms single, double, and triple bondsit is intermediate in electronegativity (2.5)it forms strong bonds with C, H, O, N, and some metals.

  • *Chapter 1. Bonding and Isomerism1.1 The Review of Atomic StructureAtomelectron(s)Atomic weight = no. of proton(s) + no. of neutron(s)Electrons are located in orbitalspossibility of electrons around the nucleus

  • Quantum Numbers*n - principal quantum number, n = 1, 2, 3, 4,

    l - azimuthal (angular momentum) quantum number, l < n (1, , n - 1)

    ml - magnetic quantum number, total ml values = 2l + 1 (-l,, 0, , l)

    ms electron spin quantum number, ms values = +, or -.

    One orbital can only hold up to two electrons (Pauli Exclusion Principle).

    Orbitals are grouped in electron shells (based on n values).

    Different orbitals have different shapes (based on l values). e.g. s sphere, l= 0; p dumbbell, l= 1.

  • *Table 1.1 Numbers of orbitals and electrons in the first three shells

  • *Shapes of Atomic OrbitalsA p- orbital consists of two lobes arranged in a straight line with the center at the nucleus.All s orbitals have the shape of a sphere, with its center at the nucleus. Of the s orbitals, 1s is the smallest, 2s is larger, and a 3s is even larger, etc.

  • *Aufbau principle for filling electrons on atomic orbitals

  • *

    Type of OrbitalsNo. of OrbitalsNo. of Electronss (l=0)1 =(2 x 0+1)2p (l=1)3 =(2 x 1+1)6d (l=2)5 =(2 x 2+1)10f (l=3)7 =(2 x 3+1)14

    Shell Number Max. No. of Electrons on the shellOrbitals (No.)12 (2 x 12)1s (1)28 (2 x 22)2s 2p (4)318 (2 x 32)3s 3p 3d (9)432 (2 x 42)4s 4p 4d 4f (16)

  • *

  • *Figure 1.1 Sodium chloride is an ionic crystal

  • *Table 1.4 Electronegativities of some common elements

  • *

  • *Figure 1.3 The molecular orbital representation of covalent bond formation

  • *Figure 1.4 Orbital overlap to form s bonds

  • *Chapter 1, Page 29 p+p = bond

  • *

  • *

  • *Resonance StructuresResonance is the use of two or more Lewis structures that differ only in the distribution of the valence electrons in representing the bonding in a species. The skeleton structure does not change; only the placement of bonds is different. We indicate resonance structures with a double-headed arrow.e.g. the Lewis structure of CO32-

    Calculate the formal charges of C and O atoms in CO32-FC (C) = 4 4 0 = 0 FC (O*) = 6 2 4 = 0 FC(O) = 6 1 6 = -1

    These Lewis structures ------ resonance structuresThe real molecule or ion is described by an average of these resonance structures.

    Benzene, C6H6

    *

  • *1.5 Symbols used in Organic Chemistry

    (1) Curved arrowscurved arrow --- used for transferring a pair of electrons

    fishhook or half-headed curved arrow --- used for transferring one electron

    (2) Straight arrowsstraight arrow --- used for pointing from reactants to products in a chemical equation double headed straight arrow --- used for converting resonance structures half headed straight arrow --- used for a reversible chemical reaction or an equilibrium1.6 Hybridization and / bonds (Review)Linus Pauling proposed the theory of orbital hybridization.(a) Hybrid orbitals can be formed by mixing s, p and / or d orbitals on an atom in order to form bonds in the molecules.(b) Hybrid orbitals have an orientation in space that matches the geometry of a molecule.(c) The number of hybrid orbitals formed is the same as the number of atomic orbitals used for the hybridization.

  • *

  • *

  • *

  • *

  • *

  • *Table 1.6 The main functional groups

  • *

  • *(c) Functional Groups Containing both Oxygen and Nitrogen (CO)NH2--- amide (primary)(d) Functional Groups Containing SulfurSH--- thiol (also mercaptane) CSC ---- thioether (also disulfide)

  • *Figure 1.11 Examples of natural acyclic compounds

  • *Figure 1.12 Examples of natural carbocyclic compunds with rings of various sizes and shapes

  • *Figure 1.13 Examples of natural heterocyclic compounds


Top Related